Performance of geopedology approach in mapping of agricultural soils within Aidoghmoush dam downstream lands in Miyaneh, Iran

ABSTRACT The geopedological method is one of the systematic methods for analyzing geomorphic surfaces in soil mapping in which field work is mainly based on work in the sample area. This research intended to investigate the degree of validity generalization of results obtained in the geopedological method for similar landforms in the Miyaneh region of East Azarbaijan Province. For this purpose, soil diversity study was conducted through measuring it in a hierarchical sequence in USDA soil taxonomy levels and by comparing similar units in the geopedological method through employing diversity and similarity indices. After preparing the initial interpretative map (based on aerial photographs) at a scale of 1:20000, the HPu211 unit that covered the greatest delineation of study area was selected and 15 soil profiles, about 150 meters apart, were excavated, described, and sampled in this unit. The degree of validity generalization of geopedological results for the mentioned unit was determined by digging nine other soil profiles in a similar unit, called the generalization area, which was located outside of the sample area. Results indicated the value of Shannon’s diversity index increased from the level of soil order to soil family in both the sample and the generalization areas; however, only at the soil family level were there significant differences between soil diversity in the two areas at the confidence level of 95%. Even by changing the understanding level, and through concentrating on the sequence of genetic horizons in the excavated profiles in the sample and generalization areas, increased soil diversity in the soil taxonomic hierarchy was proved. Therefore, it is recommended that landform phases be used, and soil family phase and/or soil series phase be determined for each landform phase, to increase the accuracy of the geopedological method.